1. Field of the Invention
The present invention relates generally to a battery charging system, and more particularly, to a smart battery charging system that considers device usage when establishing a charging plan for a battery.
2. Description of the Related Art
As mobile computing has become pervasive, portable personal computers (hereinafter referred to as portable PCs) having various sizes and functions have been developed. They include notebook PCs, handheld PCs, and PDAs.
A fundamental element that makes these devices portable is the inclusion of an internal battery which is typically rechargeable. This allows a user to operate the portable PC in an environment in which no commercial power supply is available, for instance, on a plane, outdoors, or other remote environment away from a typical office setting.
The discharging of a battery from a charged state is referred to as a single battery cycle. Thus, a non-rechargeable battery has a service life consisting of a single battery cycle, while a rechargeable battery has a service life of multiple battery cycles. Conventionally, to charge the internal battery of a portable device, a power supply is connected to the portable device, activating a charging circuit in the device to charge the battery using standard wall socket voltage. The batteries used vary in configuration and properties. For example, a lithium-ion battery has different charging requirements than does a nickel cadmium battery. Numerous other battery types are used, including nickel hydrogen batteries, lithium polymer batteries and the like. Unlike disposable non-rechargeable batteries, the rechargeable batteries used with portable devices, such as portable PCs, can be fairly expensive, usually exceeding $100–200 in cost. Thus, it is desirable to extend the service life of a battery as long as possible.
Each battery has what is considered to be an optimal charging cycle to maximize its service life. Certain battery types, for example, will have a longer service life when they are fully discharged before being subjected to recharging. Existing devices having built-in charging systems (such as laptops) do not adapt the charging cycle to match the actual use of the battery. Existing chargers typically continue charging the battery as long as the AC power cord is plugged into the computer. Little consideration is given to the conditioning of the battery and the charge/discharge cycling of the battery by the user. It simply charges to capacity and continues to be so charged until the AC power cord is unplugged.
Laptop computer users are instructed to “deep cycle” their battery to under 3% monthly in an attempt to maximize the battery service life. Compliance with these instructions is left to the battery user. In reality, computer users rarely pattern their charging cycles based on battery condition; rather, they pattern their charging cycles based upon their own use of the device. If the user wants to follow the charging suggestions of the manufacturer, they will have to schedule time to unplug the power cord and allow the battery to completely discharge, an annoying and, at times, unfeasible task.
Accordingly, a need exists for an intelligent charging system which monitors and records the usage patterns of a device in which the battery to be charged is installed, and then patterns an appropriate charging cycle for the battery based upon these usage patterns.